The goal of this contract is to provide support of National Toxicology Program (NTP) hazard identification (or hazard assessment) activities targeted toward the prevention of diseases or adverse effects caused by environmental exposure to chemical or physical agents.This contract involves the prechronic and chronic studies of 4 chemicals by the inhalation route: 1-bromopropane, cobalt metal, diethylamine and triethylamine. The 14 and 90-day studies of bromopropane, triethylamine, and diethylamine have been completed. The 2-year studies of diethylamine and 1-bromopropane are complete and reports have been submitted. The 2-year studies of triethylamine have been canceled. Cobalt metal 14 and 90 day as well as 2-year studies have been reported. Keywords Carcinogenicity;Toxicity;Bioassay;F344 rats;B6C3F1 mice;inhalation exposure;1-Bromopropane;Cobalt metal;Diethylamine;Triethylamine.